This is so, so perfect. Pal will start by trying to possess the waiter (since he has shown signs that someone is in there) and may also attempt the receptionist (since he has examined the receptionist before)

What happens to Pal's body when he uses this power?

HAHAHAHA. If left unprotected, Pal's body is an empty shell that can be possessed or harmed by outside forces--in fact, there's a canon example of a character's body being "empty" and basically being eaten by ghosts!!! Before he starts, he'll employ wards and sigils to protect his body (both ones from his own world and any that other characters remember and are willing to share) but there's still a risk.